>I was thinking of putting a precision rectifier in the sensor box,
>adding gain in the monitor box then splitting the signal into two.
>Once would go straight to the ADC for measuring the highest spikes
>while the other would go to a capacitor for electrical averaging of
>the peaks. That way I can do the fast sampling for spikes without
>the overhead of peak value discovery and averaging (20 samples per
>wave thing) and just a single sample to find the average peak.

This sounds very reasonable to me.? My color organ was built on a

precision rectifier followed by six RC integrators.? These were fed

into a quad comparator.? Let me know if you need schematics for a

precision rectifier.

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>Probably use an OPA2340 to split the (rectified) signal into two and
>add gain, then experiment from there.

Yes, I was just going to suggest a buffer before the averaging circuit.

>Oh and, I did some experimenting with PWM signals through a long
>cable. Without a resistor added, the signal was distorted. I added a
>1K resistor and the signal came out a lot cleaner. Think I'm getting
>a grasp of this cable capacitance problem. Its not so much added
>noise from the enviroment as it is the cable capacitance distorting
>the signal thats already there. Square waves turn into rounded
>corner waves and the amplitude bounces around. Less current means
>less capacitance effect, cleaner signal.

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The resistor and the capacitance of the cable will form a low-pass filter.

This one's got me perplexed because your S/N ratio will be less.? Not sure

what you mean by amplitude bouncing around.? I would suspect that your

driver circuit is not capable of driving highly capacative loads.? It may

not be putting out enough current or has a lot of ringing, etc.? Place

a 50 ohm resistor between the output of the driver in the feedback loop and

see if it drives the capacitance with more stability.

This is interesting to me, so please keep me informed.

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Good luck,